Seismic data acquisition and processing techniques are used to generate a profile (image) of a geophysical structure (subsurface) of the strata underlying the land surface or seafloor. Among other things, seismic data acquisition involves the generation of elastic waves and the collection of reflected/refracted versions of those elastic waves to generate the image. This image does not necessarily provide an accurate location for oil and gas reservoirs, but it may suggest, to those trained in the field, the presence or absence of oil and/or gas reservoirs. Thus, providing a more accurate image of the subsurface, and preferably in a shorter period of time, is an ongoing process in the field of seismic surveying.
As will be appreciated by those skilled in the art, a significant challenge in land and marine-based seismic data analysis is to calculate a velocity model for the surveyed seismic subsurface. Especially when the surveyed subsurface includes hard to illuminate formations, e.g., salts, it is difficult, if not impossible, to pick layer boundaries in a multi-layer velocity model, and thus such model cannot be updated. In this case, the geophysicist makes assumptions about the shape of the layers (or horizons) that cannot be interpreted or picked because of the lack of reflectivity or of too poor signal-to-noise ratio. For this scenario-based model update, seismic data needs to be re-migrated a large number of times before a satisfactory shape of the horizon is constructed such that it improves the image resolution in a plausible geological manner. This situation occurs in particular in the salt context, where salt boundaries cannot be picked by interpreter.
Thus, there is a need to replace or at least reduce the need for costly scenario testing where different possible horizon shapes are tried for non-pickable horizon and where seismic data for each trial is re-migrated.
Accordingly, it would be desirable to provide systems and methods that avoid the afore-described problems and drawbacks associated with velocity model building as part of an overall seismic data processing scheme.